This invention relates to a drive apparatus for driving the auxiliary equipment of a motor, and more particularly but not exclusively to the case in which the motor is the engine of an automobile.
In an automobile engine, auxiliary equipment such as charging gerators, water pumps, air conditioning compressors, and oil pumps for hydraulic steering are belt-driven by a drive pulley mounted on the end of the crankshaft. This auxiliary equipment is generally designed to be operated at relatively low speeds, and if driven at the same speed as the engine when the engine is running at high speeds, the operation of the auxiliary equipment would produce considerable power losses. Therefore, means are usually provided for adjusting the rotational speed of the drive pulley for the auxiliary equipment with respect to the rotational speed of the engine so that the auxiliary equipment can be operated at suitable speeds.
For example, Japanese Laid-Open Patent Application No. 58-200838 discloses a speed reduction apparatus for engine auxiliary equipment comprising a planetary gear reduction mechanism and a unidirectional clutch provided between an engine crankshaft and a pulley for auxiliary equipment, as well as a directly-coupled clutch comprising a hydraulic piston. At low engine speeds, the rotation of the crankshaft is transmitted directly to the pulley via the directly-coupled clutch. When the engine speed reaches a certain level, the directly-coupled clutch is disengaged, and the rotation of the crankshaft is transmitted to the pulley via the planetary gear and the one-way clutch at a reduced speed.
However, with that invention, there is a sudden change in the speed of the auxiliary equipment when the directly-coupled clutch is engaged or disengaged, which causes a shock to be imparted to both the engine and the auxiliary equipment. This shock reduces the stability of the automobile and imparts an unpleasant sensation to the driver. Furthermore, there are problems with the durability of the planetary gear reduction mechanism, and these can result in noise problems. Thus, this apparatus is not practical. Furthermore, as a planetary gear reduction mechanism is employed, the reduction ratio is not adjustable.
Japanse Laid Open Utility Model Application No. 58-86434 discloses a variable-speed driven apparatus for auxiliary equipment which utilizes two variable-pitch pulleys. A variable-pitch drive pulley is disposed on a crankshaft, and a variable-pitch driven pulley which is driven by the variable-pitch drive pulley with a belt is connected to the auxiliary equipment which is to be driven. Each variable-pitch pulley comprises a stationary portion and a movable portion which can be moved towards and away from the stationary portion in the axial direction of the pulley by a hydraulic cylinder mounted on the drive pulley so as to change the effective pitch of the pulleys, thereby adjusting the reduction ratio of the pulleys and controlling the speed of the auxiliary equipment connected to the driven pulley.
However, in that apparatus, a high-pressure oil source is necessary to operate the hydraulic cylinder, and the structure of the hydraulic actuator for the hydraulic cylinder is complicated. Furthermore, the apparatus projects by a considerable amount in the axial direction of the crankshaft of the engine, making it unsuitable for automobiles having a limited installation space such as front wheel drive automobiles in which the engine is disposed sideways.